Major Handler rewrite implementing the design's M3 acceptance
criteria ('5 concurrent viewers, all error paths correct, clean
teardown'):
Multi-viewer correctness:
- streamID -> resourceID -> Peer two-level index (was flat)
- per-stream peer cap alongside total cap, defaults match the
design's '5–8 viewer' target (8/stream, total from corewebrtc)
- per-peer awaitPeerClose goroutine watches Peer.Done() so ICE
failures yank the index entry + decrement the counter (no leaks)
- tearDownStreamPeers callback (registered with Subsystem in
NewHandler) drives all peer closes when the source process stops
Error matrix from design §6:
- 406 on codec mismatch (offer missing H264 or Opus rtpmap)
- 504 on ICE gathering timeout (passthrough from CreatePeerFromSources)
- 204 on DELETE unknown resource (idempotent per WHEP spec; was 404)
- 503 on per-stream cap reached (separate body from total-cap 503)
- 400 on missing/empty body (unchanged)
- 404 on unknown stream (unchanged)
WHEP spec compatibility:
- PATCH /whep/:id/:resource for trickle-ICE
- OPTIONS preflight on every WHEP path
- CORS Allow-Origin/Methods/Headers + Expose-Headers (Location, ETag)
- ETag header on Subscribe response
Defensive nil-peer guards in tearDown / Close paths so a partial
state doesn't panic.
Refactor: 134 -> 341 lines on handler.go but the surface is the
same (NewHandler/Register/Subscribe/Unsubscribe/Close); existing
callers continue to work. Pre-M3 test 'Unsubscribe_404WhenUnknown'
renamed and updated to the new 204 expectation.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Zac Gaetano
4d2f11d836